Expandable transluminal sheath

ABSTRACT

Disclosed is an expandable transluminal sheath, for introduction into the body while in a first, low cross-sectional area configuration, and subsequent expansion of at least a part of the distal end of the sheath to a second, enlarged cross-sectional configuration. The distal end of the sheath is maintained in the first, low cross-sectional configuration and expanded using a radial dilatation device. In an exemplary application, the sheath is utilized to provide access for a diagnostic or therapeutic procedure such as ureteroscopy or stone removal.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.13/710,762 filed Dec. 11, 2012 entitled Expandable Transluminal Sheath,which is a continuation of U.S. patent application Ser. No. 13/007,280filed Jan. 14, 2011 entitled Expandable Transluminal Sheath (now U.S.Pat. No. 8,348,892 issued Jan. 8, 2013), which is a continuation of U.S.patent application Ser. No. 11/199,566 filed Aug. 8, 2005 entitledExpandable Transluminal Sheath, which issued on Feb. 22, 2011 as U.S.Pat. No. 7,892,203, which claims priority to U.S. ProvisionalApplication Ser. No. 60/660,512, filed on Mar. 9, 2005 entitledExpandable Transluminal Sheath, and to U.S. Provisional Application Ser.No. 60/608,355, filed on Sep. 9, 2004 entitled Expandable TransluminalSheath; the entireties of which are hereby expressly incorporated hereinby reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to medical devices for transluminally accessingbody lumens and cavities and, more particularly, to methods and devicesfor accessing the mammalian urinary tract.

Description of the Related Art

A wide variety of diagnostic or therapeutic procedures involves theintroduction of a device through a natural access pathway such as a bodylumen or cavity. A general objective of access systems, which have beendeveloped for this purpose, is to minimize the cross-sectional area ofthe access lumen, while maximizing the available space for thediagnostic or therapeutic instrumentation. These procedures areespecially suited for the urinary tract of the human or other mammal.The urinary tract is relatively short and substantially free from thetortuosity found in many endovascular applications.

Ureteroscopy is an example of one type of therapeutic interventionalprocedure that relies on a natural access pathway, which is the urethra,the bladder, which is a body cavity, and the ureter, another body lumen.Ureteroscopy is a minimally invasive procedure that can be used toprovide access to the upper urinary tract, specifically the ureter andkidney. Ureteroscopy is utilized for procedures such as stoneextraction, stricture treatment, or stent placement. Other types oftherapeutic interventional procedures suitable for use with expandablesheath technology include endovascular procedures such as introductionof cardiac valve replacements or repair devices via a percutaneousaccess to the vasculature. Gastrointestinal procedures, againpercutaneously performed, include dilation of the common bile duct andremoval of gallstones.

To perform a procedure in the ureter, a cystoscope is placed into thebladder through the urethra. A guidewire is next placed, through theworking channel of the cystoscope and under direct visual guidance, intothe target ureter. Once guidewire control is established, the cystoscopeis removed and the guidewire is left in place. A ureteral sheath orcatheter is next advanced through the urethra over the guidewire,through the bladder and on into the ureter. The guidewire may now beremoved to permit instrumentation of the ureteral sheath or catheter. Adifferent version of the procedure involves leaving the guidewire inplace and passing instrumentation alongside or over the guidewire. Inyet another version of the procedure, a second guidewire or “safetywire” may be inserted into the body lumen or cavity and left in placeduring some or all of the procedure.

Certain current techniques involve advancing a flexible, 10 to 18French, ureteral sheath or catheter with integral flexible, taperedobturator over the guidewire. Because axial pressure is required toadvance and place each catheter, care must be taken to avoid kinking thesheath, catheter, or guidewire during advancement so as not tocompromise the working lumen of the catheter through whichinstrumentation, such as ureteroscopes and stone extractors, can now beplaced. The operator must also exercise care to avoid advancing thesheath or catheter against strictures or body lumen or cavity walls withsuch force that injury occurs to said body lumen or cavity walls.

One of the issues that arise during ureteroscopy is the presence of anobstruction or stenosis in the ureter, which is sometimes called astricture, that prohibits a sheath or catheter with a sufficiently largeworking channel from being able to be advanced into the ureter. Suchconditions may preclude the minimally invasive approach and require moreinvasive surgical procedures in order to complete the task. Urologistsmay be required to use sheaths or catheters with suboptimal centrallumen size because they are the largest catheters that can be advancedto the proximal end of the ureter. Alternatively, urologists may startwith a larger catheter and then need to downsize to a smaller catheter,a technique that results in a waste of time and expenditure. Finally, aurologist may need to dilate the ureter with a dilation system beforeplacing the current devices, again a waste of time and a need formultiple devices to perform the procedure. In most cases, it isnecessary for the urologist to perform fluoroscopic evaluation of theureter to determine the presence or absence of strictures and what sizecatheter would work for a given patient.

Additional information regarding ureteroscopy can be found in Su, L, andSosa, R. E., Ureteroscopy and Retrograde Ureteral Access, Campbell'sUrology, 8th ed, vol. 4, pp. 3306-3319 (2002), Chapter 97. Philadelphia,Saunders, and Moran, M. E., editor, Advances in Ureteroscopy, UrologicClinics of North America, vol. 31, No. 1 (February 2004).

SUMMARY OF THE INVENTION

A need therefore remains for improved access technology, which allows adevice to be transluminally passed through a relatively small diameterduct, while accommodating the introduction of relatively large diameterinstruments. It would be beneficial if a urologist did not need toinventory and use a range of catheter diameters. It would be far moreuseful if one catheter diameter could fit the majority of patients.Ideally, the catheter would be able to enter a vessel or body lumen witha diameter of 6 to 10 French or smaller, and be able to pass instrumentsthrough a central lumen that was 12 to 18 French. These requirementsappear to be contradictory but can be resolved by an embodiment of theinvention described herein. Advantageously the sheath would also bemaximally visible under fluoroscopy and would be relatively inexpensiveto manufacture. The sheath or catheter would preferably be kinkresistant and minimize abrasion and damage to instrumentation beingpassed therethrough. Preferably, the sheath or catheter would furtherminimize the potential for injury to body lumen or cavity walls orsurrounding structures. Such damage could potentially lead tostrictures, leakage of body lumen or cavity contents into surroundingspaces, contamination, hemorrhage, or the like.

Accordingly, one embodiment of the present invention comprise using aradially expanding access sheath to provide access to the ureter,kidney, or bladder. In one such embodiment, the sheath would have anintroduction outside diameter that ranged from 4 to 12 French with apreferred range of 5 to 10 French. The diameter of the sheath would beexpandable to permit instruments ranging up to 60 French to passtherethrough, with a preferred range of between 3 and 20 French. Theability to pass the large instruments through a catheter introduced witha small outside diameter is derived from the ability to expand thedistal end of the catheter to create a larger through lumen. Theexpandable distal end of the catheter can comprise 75% or more of theoverall working length of the catheter. The proximal end of the catheteris generally larger to provide for pushability, control, and the abilityto pass large diameter instruments therethrough.

Another embodiment of the present invention comprises a transluminalaccess system for providing minimally invasive access to anatomicallyproximal structures. The system includes an access sheath comprising anaxially elongate tubular body that defines a lumen extending from theproximal end to the distal end of the sheath. At least a portion of thedistal end of the elongate tubular body is expandable from a first,smaller cross-sectional profile to a second, greater cross-sectionalprofile. In such an embodiment, the first, smaller cross-sectionalprofile is created by making axially oriented folds in the sheathmaterial. These folds may be located in only one circumferentialposition on the sheath, or there may be a plurality of such folds orlongitudinally oriented crimps in the sheath. The folds or crimps may bemade permanent or semi-permanent by heat-setting the structure, oncefolded. In one embodiment, a releasable jacket is carried by the accesssheath to restrain at least a portion of the elongate tubular structurein the first, smaller cross-sectional profile. In another embodiment,the jacket is removed prior to inserting the sheath into the patient. Insome embodiments, the elongate tubular body is sufficiently pliable toallow the passage of objects having a maximum cross-sectional diameterlarger than an inner diameter of the elongate tubular body in thesecond, greater cross-sectional profile. The adaptability to objects oflarger dimension is accomplished by re-shaping of the cross-section tothe larger dimension in one direction accompanied by a reduction indimension in a lateral direction. The adaptability may also be generatedthrough the use of malleable or elastomerically deformable sheathmaterial.

In another embodiment of the invention, a transluminal access sheathassembly for providing minimally invasive access comprises an elongatetubular member having a proximal end and a distal end and defines aworking inner lumen. In this embodiment, the tubular member comprises afolded or creased sheath that is expanded by a dilatation balloon. Thedilatation balloon, can be filled with fluids at appropriate pressure,to generate the force to expand the sheath. The dilatation balloon ispreferably removable to permit subsequent instrument passage through thesheath. In some embodiments, longitudinal runners may be disposed withinthe sheath to serve as tracks for instrumentation, which furtherminimize friction while minimizing the risk of catching the instrumenton the expandable plastic tubular member. Such longitudinal runners arepreferably circumferentially affixed within the sheath so as not toshift out of alignment. In yet another embodiment, the longitudinalrunners may be replaced by longitudinally oriented ridges and valleys,termed flutes. The flutes, or runners, can be oriented along thelongitudinal axis of the sheath, or they can be oriented in a spiral, orrifled, fashion.

In each of the embodiments, the proximal end of the access assembly,apparatus, or device is preferably fabricated as a structure that isflexible, resistant to kinking, and further retains both column strengthand torqueability. Such structures can include, but are not limited to,tubes fabricated with coils or braided reinforcements and preferablycomprise inner walls that prevent the reinforcing structures fromprotruding, poking through, or becoming exposed to the inner lumen ofthe access apparatus. Such proximal end configurations may be singlelumen, or multi-lumen designs, with a main lumen suitable for instrumentor obturator passage and additional lumens being suitable for controland operational functions such as balloon inflation. Such proximal tubeassemblies can be affixed to the proximal end of the distal expandablesegments described heretofore. In an embodiment, the proximal end of thecatheter includes an inner layer of thin polymeric material, an outerlayer of polymeric material, and a central region comprising a coil,braid, stent, plurality of hoops, or other reinforcement. In such anembodiment, it is beneficial to create a bond between the outer andinner layers at a plurality of points, most preferably at theinterstices or perforations in the reinforcement structure, which isgenerally fenestrated. Such bonding between the inner and outer layerscauses a braided structure to lock in place. In another embodiment, theinner and outer layers are not fused or bonded together in at leastsome, or all, places. When similar materials are used for the inner andouter layers, the sheath structure can advantageously be fabricated byfusing of the inner and outer layer to create a uniform, non-layeredstructure surrounding the reinforcement. The polymeric materials usedfor the outer wall of the jacket are preferably elastomeric to maximizeflexibility of the catheter. The polymeric materials used in thecomposite catheter inner wall may be the same materials as those usedfor the outer wall, or they may be different. In another embodiment, acomposite tubular structure can be co-extruded by extruding a polymericcompound with a braid or coil structure embedded therein. Thereinforcing structure is preferably fabricated from annealed metals,such as fully annealed stainless steel, titanium, or the like. In thisembodiment, once expanded, the folds or crimps can be held open by thereinforcement structure embedded within the sheath, wherein thereinforcement structure is malleable but retains sufficient force toovercome any forces imparted by the sheath tubing.

In certain embodiments of the invention, it is beneficial that thesheath comprise a radiopaque marker or markers. The radiopaque markersmay be affixed to the non-expandable portion or they may be affixed tothe expandable portion. Markers affixed to the radially expandableportion preferably do not restrain the sheath or catheter from radialexpansion or collapse. Markers affixed to the non-expandable portion,such as the catheter shaft of a balloon dilator may be simple rings thatare not radially expandable. Radiopaque markers include shapesfabricated from malleable material such as gold, platinum, tantalum,platinum iridium, and the like. Radiopacity can also be increased byvapor deposition coating or plating metal parts of the catheter withmetals or alloys of gold, platinum, tantalum, platinum-iridium, and thelike. Expandable markers may be fabricated as undulated or wavy rings,bendable wire wound circumferentially around the sheath, or otherstructures such as are found commonly on stents, grafts or cathetersused for endovascular access in the body. Expandable structures may alsoinclude dots or other incomplete surround shapes affixed to the surfaceof a sleeve or other expandable shape. Non-expandable structures includecircular rings or other structures that completely surround the cathetercircumferentially and are strong enough to resist expansion. In anotherembodiment, the polymeric materials of the catheter or sheath, includingthose of the sheath composite wall, may be loaded with radiopaque fillermaterials such as, but not limited to, bismuth salts, or barium salts,or the like, at percentages ranging from 1% to 50% by weight in order toincrease radiopacity.

In order to enable radial or circumferential expansive translation ofthe reinforcement, it may be beneficial not to completely bond the innerand outer layers together, thus allowing for some motion of thereinforcement in translation as well as the normal circumferentialexpansion. Regions of non-bonding may be created by selective bondingbetween the two layers or by creating non-bonding regions using a sliplayer fabricated from polymers, ceramics or metals. Radial expansioncapabilities are important because the proximal end needs to transitionto the distal expansive end and, to minimize manufacturing costs, thesame catheter may be employed at both the proximal and distal end, withthe expansive distal end undergoing secondary operations to permitradial or diametric expansion.

In another embodiment, the distal end of the catheter is fabricatedusing an inner tubular layer, which is thin and lubricious. This innerlayer is fabricated from materials such as, but not limited to, FEP,PTFE, polyamide, polyethylene, polypropylene, Pebax, Hytrel, and thelike. Radiopaque filler materials can be added to the polymer innerlayer during extrusion to enhance visibility under fluoroscopy. Thereinforcement layer comprises a coil, braid, stent, or plurality ofexpandable, foldable, or collapsible rings, which are generallymalleable and maintain their shape once deformed. Preferred materialsfor fabricating the reinforcement layer include but are not limited to,stainless steel, tantalum, gold, platinum, platinum-iridium, titanium,nitinol, and the like. The materials are preferably fully annealed or,in the case of nitinol, fully martensitic. The outer layer is fabricatedfrom materials such as, but not limited to, FEP, PTFE, polyamide,polyethylene, polypropylene, polyurethane, Pebax, Hytrel, and the like.The inner layer is fused or bonded to the outer layer through holes inthe reinforcement layer to create a composite unitary structure. Thestructure is crimped radially inward to a reduced cross-sectional area.A balloon dilator is inserted into the structure before crimping orafter an initial crimping and before a final sheath crimping. Theballoon dilator is capable of forced expansion of the reinforcementlayer, which provides sufficient strength necessary to overcome anyforces imparted by the polymeric tubing.

Another embodiment of the invention comprises a method of providingtransluminal access. The method comprises inserting a cystoscope into apatient, transurethrally, into the bladder. Under direct opticalvisualization, fluoroscopy, MRI, or the like, a guidewire is passedthrough the instrument channel of the cystoscope and into the bladder.The guidewire is manipulated, under the visual control described above,into the ureter through its exit into the bladder. The guidewire is nextadvanced to the appropriate location within the ureter. The cystoscopeis next removed, leaving the guidewire in place. The ureteral accesssheath is next advanced over the guidewire transurethrally so that itsdistal tip is now resident in the ureter or the kidney. The position ofthe guidewire is maintained carefully so that it does not come out ofthe ureter and fall into the bladder. The removable dilator comprisesthe guidewire lumen, and is used to guide placement of the access sheathinto the urinary lumens. Expansion of the distal end of the accesssheath from a first smaller diameter cross-section to a second largerdiameter cross-section is next performed, using the balloon dilator. Theballoon dilator is subsequently removed from the sheath to permitpassage of instruments that would not normally have been able to beinserted into the ureter due to the presence of strictures, stones, orother stenoses. The method further optionally involves releasing theelongate tubular body from a constraining tubular jacket, removing theexpandable member from the elongate tubular body; inserting appropriateinstrumentation, and performing the therapeutic or diagnostic procedure.Finally, the procedure involves removing the elongate tubular body fromthe patient. Once the sheath is in place, the guidewire may be removedor, preferably, it may be left in place. Alternatively, a secondguidewire, or safety wire, can be introduced into the ureter and beplaced alongside or through the sheath.

In one embodiment, where the transluminal access sheath is used toprovide access to the upper urinary tract, the access sheath may be usedto provide access by tools adapted to perform biopsy, urinary diversion,stone extraction, antegrade endopyelotomy, and resection of transitionalcell carcinoma and other diagnostic or therapeutic procedures of theupper urinary tract or bladder. Other applications of the transluminalaccess sheath include a variety of diagnostic or therapeutic clinicalsituations, which require access to the inside of the body, througheither an artificially created, percutaneous access, or through anothernatural body lumen.

For purposes of summarizing the invention, certain aspects, advantagesand novel features of the invention are described herein. It is to beunderstood that not necessarily all such advantages may be achieved inaccordance with any particular embodiment of the invention. Thus, forexample, those skilled in the art will recognize that the invention maybe embodied or carried out in a manner that achieves one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein. These and other objectsand advantages of the present invention will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various features of theinvention will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the invention and not to limit the scope of theinvention. Throughout the drawings, reference numbers are re-used toindicate correspondence between referenced elements.

FIG. 1 is a front view schematic representation of the urethra, bladder,ureter, and kidneys;

FIG. 2 is a front view schematic representation of the urethra, bladder,ureter, and kidneys with a catheter passed into the ureter by way of theurethra;

FIG. 3A is a cross-sectional illustration of an embodiment of a radiallyexpandable transluminal catheter or sheath comprising a tube that isfolded, at its distal end in longitudinal creases, a balloon dilator,and an outer retaining sleeve, the sheath tube and dilator being intheir radially collapsed configuration;

FIG. 3B is a partial cross-sectional illustration of the radiallyexpandable transluminal sheath of FIG. 3A, wherein the sheath and thedilator are in their radially expanded configuration,

FIG. 3C illustrates a side view of the radially expanded transluminalsheath of FIG. 3B, wherein the dilator has been removed, according to anembodiment of the invention;

FIG. 4 illustrates a side view of another embodiment of a radiallyexpandable transluminal catheter or sheath comprising a removable shroudcovering the distal expandable region, according to an embodiment of thepresent invention;

FIG. 5A is an illustration of another embodiment of a radiallyexpandable transluminal sheath further comprising a plurality oflongitudinally disposed runners;

FIG. 5B illustrates a side view of the radially expandable sheath ofFIG. 5A wherein the internal balloon dilator has expanded the distalportion of the sheath;

FIG. 5C illustrates a lateral cross-section of the distal portion of thetransluminal sheath of FIG. 5A wherein the sheath covering comprisesflutes or longitudinally disposed lines of increased thickness;

FIG. 6A illustrates a side cutaway view of another embodiment of aradially collapsed sheath comprising an expandable distal region withone or more longitudinal folds and a malleable coil reinforcing layerembedded within the distal region;

FIG. 6B illustrates the sheath of FIG. 6A, with cutaway sections,wherein the balloon has expanded the distal region of the sheath to itsfully expanded configuration;

FIG. 7A illustrates another embodiment of a radially expandabletransluminal sheath comprising a malleable expandable stent-likereinforcement, a balloon dilator, and an unfolding sleeve with thedistal end of the sheath, comprising this structure, is crimped orcompressed radially inward for delivery to the patient;

FIG. 7B illustrates the radially expandable transluminal sheath of FIG.7A wherein the distal section has been expanded by the balloon dilator;

FIG. 8A illustrates another embodiment of a radially expandabletransluminal sheath comprising a dilatation balloon, a malleable,reinforced, folded, expandable distal end, a braid reinforced proximalend;

FIG. 8B illustrates an enlarged view of the distal tip of the distalregion of the sheath of FIG. 8A with a breakaway of the outer layershowing the reinforcing layer, the inner layer, and the expandableradiopaque marker;

FIG. 9A illustrates the distal end of an embodiment of a radiallyexpandable transluminal sheath with a step transition from the distaledge of the sheath and the balloon dilator;

FIG. 9B illustrates the distal end of the radially expandabletransluminal sheath of FIG. 9A wherein a fairing sleeve has been addedto the dilator to smooth the step transition;

FIG. 9C illustrates the distal end of the radially expandabletransluminal sheath of FIG. 9B, wherein the sheath has been expanded bya dilatation balloon, the fairing sleeve has slipped off the sheathdistal edge and now resides against the outside of the dilatationballoon;

FIG. 10A illustrates a lateral cross-section of an embodiment of asheath tube configured with discreet thin areas, running longitudinallyalong the tube;

FIG. 10B illustrates a lateral cross-section of the sheath tube of FIG.10A which has been folded at the thin areas to create a smaller diametertube;

FIG. 10C illustrates a lateral cross-section of the sheath tube of FIG.10B, which has been folded down over a balloon, which has further beenfolded into four flaps and has been compressed against its centraltubing;

FIG. 10D illustrates a lateral cross-section of an embodiment of asheath tube comprising an inner lubricious layer, a reinforcing layer,an intermediate elastomeric layer, and an outer lubricious layer;

FIG. 10E illustrates a lateral cross-section of an embodiment of anexpandable sheath tube comprising a double longitudinal fold;

FIG. 11A illustrates a side view of an embodiment of a sheath sheathcomprising split ring reinforcement, with its distal end collapsedradially;

FIG. 11B illustrates a radially expandable sheath with split ringreinforcement as in FIG. 11A, wherein the distal end has been expanded;

FIG. 12 illustrates the distal end of an embodiment of a radiallyexpandable sheath with a fairing internal to the balloon;

FIG. 13A illustrates the proximal end of an embodiment of radiallyexpandable sheath for endovascular use further comprising a valveintegral to the sheath hub and a valve connected to the dilator hub;

FIG. 13B illustrates the proximal end of an embodiment of a radiallyexpandable sheath for laparoscopic use, further comprising a valveintegral to the sheath hub, according to an embodiment of the invention;and

FIG. 14 illustrates a cross-sectional view of the proximal end of aanother embodiment of a radially expandable sheath hub and dilator hub.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the FIGS. 1-14, various embodiments of a catheter or asheath will be described. A catheter or a sheath, can be described asbeing an axially elongate hollow substantially tubular structure havinga proximal end and a distal end. The axially elongate structure furtherhas a longitudinal axis and preferably has an internal through lumenthat can extend from the proximal end to the distal end for the passageof instruments, implants, fluids, tissue, or other materials. Theaxially elongate hollow tubular structure is preferably generallyflexible and capable of bending, to a greater or lesser degree, throughone or more arcs in one or more directions perpendicular to the mainlongitudinal axis. In many embodiments, the tubular structure and theinternal lumen have a substantially circular cross-section but in otherembodiments the cross-section can have another shape (e.g., oval,rectangular etc.)

As is commonly used in the art of medical devices, the proximal end ofthe device is that end that is closest to the user, typically a surgeonor interventionalist. The distal end of the device is that end closestto the patient or that is first inserted into the patient. A directionbeing described as being proximal to a certain landmark will be closerto the surgeon, along the longitudinal axis, and further from thepatient than the specified landmark. The diameter of a catheter is oftenmeasured in “French Size” which can be defined as 3 times the diameterin millimeters (mm). For example, a 15 French catheter is 5 mm indiameter. The French size is designed to approximate the circumferenceof the catheter in mm and is often useful for catheters that havenon-circular cross-sectional configurations. While the originalmeasurement of “French” used pi (3.14159 . . . ) as the conversionfactor between diameters in mm and French, the system has evolved todayto where the conversion factor is exactly 3.0.

FIG. 1 is a schematic frontal illustration of a urinary system 100 ofthe human comprising a urethra 102, a bladder 104, a plurality ofureters 106, a plurality of kidneys 110 and a plurality of entrances 114to the ureter from the bladder. In this illustration, the leftanatomical side of the body is toward the right of the illustration.

Referring to FIG. 1, the urethra 102 is lined on its interior byurothelium. Generally, the internal surfaces of the urethra 102, thebladder 104, and ureters 106 are considered mucosal tissue. The urethra102 is relatively short in women and may be long in men since it runsthrough the entire length of the penis. The circumference of theunstretched urethra 102 is generally in the range of pi times 8 mm, or24 mm, although the urethra 102 generally approximates thecross-sectional shape of a slit when no fluid or instrumentation isresident therein. The bladder 104 has the capability of holding between100 and 300 cc of urine or more. The volume of the bladder 104 increasesand decreases with the amount of urine that fills therein. During aurological procedure, saline is often infused into the urethra 102 andbladder 104 thus filling the bladder 104. The general shape of thebladder 104 is that of a funnel with a dome shaped top. Nervous sensorsdetect muscle stretching around the bladder 104 and a person generallyempties their bladder 104, when it feels full, by voluntarily relaxingthe sphincter muscles that surround the urethra 102. The ureters 106operably connect the kidneys 110 to the bladder 104 and permit drainageof urine that is removed from the blood by the kidneys 110 into thebladder 104. The diameter of the ureters 106 in their unstretchedconfiguration approximates a round tube with a 4 mm diameter, althoughtheir unstressed configuration may range from round to slit-shaped. Theureters 106 and the urethra 102 are capable of some expansion with theapplication of internal forces such as a dilator, etc. The entrances 114to each of the ureters 106, of which there are normally two, are locatedon the wall of the bladder 104 in the lower region of the bladder 104.

FIG. 2 is a schematic frontal illustration, looking in the posteriordirection from the anterior direction, of the urinary system 100comprising the urethra 102, the bladder 104, a plurality of ureters 106having entrances 114, a plurality of kidneys 110, a stricture 202 in theleft ureter, and further comprising a catheter 204 extending from theurethra 102 into the right kidney 110. In this illustration, the leftanatomical side of the body is toward the right of the illustration.

Referring to FIG. 2, the stricture 202 may be the result of apathological condition such as an infection. The stricture may also bethe result of iatrogenic injury such as that attributed to a surgicalinstrument or catheter that caused damage to the wall of the ureter 106.The stricture 202 may be surrounded by fibrous tissue and may preventthe passage of instrumentation that would normally have passed through aureter 106. The catheter 204 is exemplary of the type used to access theureter 106 and the kidney 110, having been passed transurethrally intothe bladder 104 and on into the ureter 106. A catheter routed from theurethra 102 into one of the ureters 106 may turn a sharp radius withinthe open unsupported volume of the bladder 104. The radius of curvaturenecessary for a catheter to turn from the urethra 102 into the ureter106 may be between 1 cm and 10 cm and in most cases between 1.5 cm and 5cm. The catheter is generally first routed into the ureter 106 along aguidewire that is placed using a rigid cystoscope. The rigid cystoscope,once it is introduced, straightens out the urethra 102 and is aimedclose to the entrance 114 to the ureter 106 to facilitate guidewireplacement through the working lumen of the cystoscope.

FIG. 3A illustrates a longitudinal view of an embodiment of anexpandable transluminal sheath 300 adapted for use in the urinary system100 of FIGS. 1 and 2. The front (distal) section of the sheath 300 isdepicted in exterior view and not in cross-section. The proximal region302 and the central region are shown in longitudinal cross-section. Thetransluminal sheath 300 comprises a proximal end 302 and a distal end304. In the illustrated embodiment, the proximal end 302 furthercomprises a proximal sheath tube 306, a sheath hub 308, an optionalsleeve 310, an optional sleeve grip 312, an inner catheter shaft 318, anouter catheter shaft 324, and a catheter hub 316. The catheter hub 316further comprises the guidewire access port 332. The catheter shaft 318further comprises a guidewire lumen 334. The distal end 304 furthercomprises a distal sheath tube 322, the inner catheter shaft 318, and aballoon 320. The distal sheath tube 322 is folded longitudinally intoone, or more, creases 328 to reduce the tubes 322 cross-sectionalprofile. The sheath hub 308 further comprises a distally facing surface340, a proximally facing surface 342, a tapered distal edge 344, and atie-down grommet 346.

Referring to FIG. 3A, the proximal end 302 generally comprises theproximal sheath tube 306 that can be permanently affixed or otherwisecoupled to the sheath hub 308. The optional sleeve 310 is tightlywrapped around the proximal sheath tube 306 and is generally able to besplit lengthwise and be removed or disabled as a restraint by pulling onthe optional sleeve grip 312 that is affixed to the sleeve 310. Theoptional sleeve 310 is preferably fabricated from transparent material,or material with a color other than that of the sheath 300, and is shownso in FIGS. 3A and 3B. The proximal end further comprises the innercatheter shaft 318, the outer catheter shaft 324, and the catheter hub316. The catheter hub 316 is integrally molded with, welded to, bondedor otherwise coupled, to the guidewire port 332. The dilator, orcatheter, hub 316 allows for gripping the dilator and it allows forexpansion of the dilatation balloon 320 by pressurizing an annulusbetween the inner catheter shaft 318 and the outer catheter shaft 324,said annulus having openings into the interior of the balloon 320. Theballoon 320 is preferably bonded, at its distal end, either adhesivelyor by fusion, using heat or ultrasonics, to the inner catheter shaft318. The proximal end of the balloon 320 is preferably bonded or weldedto the outer catheter shaft 324. In another embodiment, pressurizationof the balloon 320 can be accomplished by injecting fluid, underpressure, into a separate lumen in the inner or outer catheter shafts318 or 324, respectively, said lumen being operably connected to theinterior of the balloon 320 by openings or scythes in the cathetertubing. Such construction can be created by extruding a multi-lumentube, rather than by nesting multiple concentric tubes. The distal end304 generally comprises the distal sheath tube 322 which is folded intocreases 328 running along the longitudinal axis and which permit thearea so folded to be smaller in diameter than the sheath tube 306. Theinner catheter shaft 318 comprises a guidewire lumen 334 that may beaccessed from the proximal end of the catheter hub 316 and preferablypasses completely through to the distal tip of the catheter shaft 318.The guidewire lumen 334 is able to slidably receive guidewires up to andincluding 0.038-inch diameter devices.

As mentioned above, the proximal end of the sheath 300 comprises thesheath hub 308 and the dilator hub 316. In one embodiment, the dilatorhub 316 is keyed so that when it is interfaced to, or attached to, thesheath hub 308, the two hubs 308 and 316 cannot rotate relative to eachother. This is beneficial so that the balloon 320 or the dilator shaft318 do not become twisted due to inadvertent rotation of the dilator hub316 relative to the sheath hub 308. A twisted balloon 320 has thepotential of not dilating fully because the twist holds the balloon 320tightly to the dilator shaft 318 and prevents fluid from fully fillingthe interior of the balloon 320. Twisting of the dilator shaft 318 orballoon 320 has the potential for restricting guidewire movement withinthe guidewire lumen 334 or adversely affecting inflation/deflationcharacteristics of the balloon 320. Thus, the anti-rotation feature ofthe two hubs 308 and 316 can be advantageous in certain embodiments. Theanti-rotation features could include mechanisms such as, but not limitedto, one or more keyed tab on the dilator hub 316 and one or morecorresponding keyed slot in the sheath hub 308.

In the illustrated embodiment, axial separation motion between thedilator hub 316 and the sheath hub 308 easily disengages the two hubs308 and 316 while rotational relative motion is prevented by thesidewalls of the tabs and slots. A draft angle on the sidewalls of thetabs and the slots further promotes engagement and disengagement of theanti-rotation feature. In another embodiment, the sheath hub 308 isreleaseably affixed to the dilator hub 316 so the two hubs 308 and 316are coaxially aligned and prevented from becoming inadvertantlydisengaged or separated laterally. In this embodiment, the two hubs 308and 316 are connected at a minimum of 3 points, which prevent lateralrelative motion in both of two substantially orthogonal axes. In apreferred embodiment, the two hubs 308 and 316 are engaged substantiallyaround their full 360-degree perimeter. Manual pressure is sufficient tosnap or connect the two hubs 308 and 316 together as well as to separatethe two hubs 308 and 316.

In another embodiment, the distal end of the sheath hub 308 isconfigured to taper into the sheath tubing 306 at the distal taper 344so that the sheath hub 308 distal end 344 and the proximal end of thesheath tubing 306 can be advanced, at least partly, into the urethra orurethral meatus without causing tissue damage. The sheath hub 308 servesas the handle for the sheath 300 and is generally a cylinder ofrevolution with certain changes in outside diameter moving from distalto proximal end. In the illustrated embodiment, the distal facingsurface 340 of the sheath hub 308 can define a cone tapering inwardmoving increasingly distally. The cone, in longitudinal cross-section,can be characterized by two exterior walls, symmetrically disposed abouta centerline, each of said exterior walls being curvilinear anddescribing a concave outline. In a preferred embodiment, the exterioroutline of the distal surface 340 of the sheath hub 308 can describe alinear outline, with surfaces running generally parallel to thelongitudinal axis of the sheath tubing 306 and other surfaces runninggenerally perpendicular to the longitudinal axis of the sheath tubing306. In this preferred embodiment, there are no curvilinear axialcross-sectional outlines except at regions of fillets or other roundingto substantially eliminate any sharp edges that could cut through glovesor fingers. The proximally facing surface 342 of the sheath hub 308 canbe curvilinear and flared with a longitudinal cross-section outlineappearing like the internal surface of a bell, such shape acting as afunnel for instrumentation. In this embodiment, the axialcross-sectional view of the distally facing surface 342 describes twointerior walls, symmetrically disposed about a centerline, each of thewalls being convex when viewed from the proximal end of the sheath 300.In a preferred embodiment, the proximally facing surface 342 of thesheath hub 308 can appear substantially linear with edges that areoriented substantially perpendicular to the longitudinal axis of thesheath tubing 306. The access through the proximal surface 342 of thesheath hub 308 to the inner lumen of the sheath 300, can be curvilinearand flared, or it can be linear and describe a lumen that is generallyparallel to the longitudinal axis. In another embodiment, the accessport through the proximal end 342 of the sheath hub 308 can comprise astraight taper, such as a 6 percent Luer taper to allow for sealing withother devices inserted therein or to allow for ease of device insertion.The amount of end taper can vary between 1-½ degrees and 20 degreesbetween each side and the longitudinal axis of the sheath 300. Themaximum outer diameter of the sheath hub 308 can be between 0.25 and 2.0inches, with a preferred range of between 0.5 and 1.0 inches. The sheathhub 308 can be sized so that at least half a finger diameter is cradledby each side of the flange of the hub 308. The distally facing surface340 of the sheath hub 308 can furthermore be shaped to havesubstantially the same curve radius as a finger, so as to be received,or grasped, between two fingers of the hand, cigarette style, like thetechnique used for control of cystoscopes. In another embodiment, thesheath hub 308 can be sized and configured to be grasped between a thumband finger, like a pencil or catheter, where there are no features orcurves on the distally facing surface 340 of the sheath hub 308 toapproximately match or conform to the shape or diameter of two fingers.

In the illustrated embodiment of FIG. 3A, the distal end 304 of thedevice comprises the catheter shaft 318 and the dilatation balloon 320.The catheter hub 316 may removably lock onto the sheath hub 308 toprovide increased integrity to the system and maintain longitudinalrelative position between the catheter shaft 318 and the sheath tubing322 and 306. The catheter hub 316 can have a taper leading from theproximal outside end into any internal or through lumens. The cathetershaft 318 and the balloon 320 are slidably received within the proximalsheath tube 306. The catheter shaft 318 and balloon 320 are slidablyreceived within the distal sheath tube 322 when the distal sheath tube322 is radially expanded but are frictionally locked within the distalsheath tube 322 when the tube 322 is radially collapsed. The outsidediameter of the distal sheath tube 322 ranges from about 4 French toabout 16 French in the radially collapsed configuration with a preferredsize range of about 5 French to about 10 French. The outside diameter isan important parameter for introduction of the device. Once expanded,the distal sheath tube 322 has an inside diameter ranging from about 8French to about 20 French. In many applications, the inside diameter ismore important than the outside diameter once the device has beenexpanded. The wall thickness of the sheath tubes 306 and 322 can rangefrom about 0.002 to about 0.030 inches with a preferred thickness rangeof about 0.005 to about 0.020 inches.

FIG. 3B illustrates a cross-sectional view of the sheath 300 of FIG. 3Awherein the balloon 320 has been inflated causing the sheath tube 322 atthe distal end 304 to expand and unfold the longitudinal creases orfolds 328. Preferably, the distal sheath tube 322 has the properties ofbeing able to bend or yield, especially at crease lines, and maintainits configuration once the forces causing the bending or yielding areremoved. The proximal sheath tube 306 is can be affixed to the sheathhub 308 by insert molding, bonding with adhesives, welding, or the like.As mentioned above, the balloon 320 can be been inflated by pressurizingthe annulus between the inner tubing 318 and the outer tubing 324 byapplication of an inflation device at the inflation port 330 which isintegral to, bonded to, or welded to the catheter hub 316. Thepressurization annulus empties into the balloon 320 at the distal end ofthe outer tubing 324. Exemplary materials for use in fabrication of thedistal sheath tube 322 include, but are not limited to,polytetrafluoroethylene (PTFE), fluorinated ethylene polymer (FEP),polyethylene, polypropylene, polyethylene terephthalate (PET), and thelike. A wall thickness of 0.008 to 0.012 inches is generally suitablefor a device with a 16 French OD while a wall thickness of 0.019 inchesis appropriate for a device in the range of 36 French OD. In oneembodiment, the resulting through lumen of the sheath 300 is generallyconstant in French size going from the proximal end 302 to the distalend 304. The balloon 320 can be fabricated by techniques such as stretchblow molding from materials such as polyester, polyamide, irradiatedpolyethylene, and the like.

FIG. 3C illustrates a side cross-sectional view of the sheath 300 ofFIG. 3B wherein the catheter shaft 318, the balloon 320, and thecatheter hub 316 have been withdrawn and removed leaving the proximalend 302 and the distal end 304 with a large central lumen capable ofholding instrumentation. The sleeve 310 and the sleeve grip 312 havealso been removed from the sheath 300. The shape of the distal sheathtube 322 may not be entirely circular in cross-section, followingexpansion, but it is capable of carrying instrumentation the same sizeas the round proximal tube 306. Because it is somewhat flexible andfurther is able to deform, the sheath 300 can hold noncircular objectswhere one dimension is even larger than the round inner diameter of thesheath 300. The balloon 320 is preferably deflated prior to removing thecatheter shaft 318, balloon 320 and the catheter hub 316 from the sheath300.

FIG. 4 illustrates a side view of another embodiment of a radiallyexpandable sheath 300 comprising a shroud 400. The shroud 400 is removedfrom the sheath 300 prior to insertion of the sheath 300 into the bodylumen or cavity. In this embodiment, the shroud 400 is slidably affixedover the distal end of the distal sheath tube 322 after folding has beencompleted. The shroud 400, in this embodiment, is closed at its mostdistal end and must be removed prior to the procedure in order toadvance the sheath 300 distally over a guidewire. The shroud 400 can befabricated from polymeric tubing such as, but not limited topolyethylene, polypropylene, FEP, PTFE, polyurethane, polyamide, and thelike. The inner diameter of the shroud 400 is the same as, or onlyslightly larger, for example 0.001 to 0.020 inches larger, than theouter diameter of the folded distal sheath tube 322. The wall thicknessof the shroud 400 can be between 0.0005 and 0.10 inches and preferablyrange between 0.004 and 0.020 inches. The shroud 400 further comprises aplug or closure 402 at the distal end to prevent guidewire passagetherethrough. The plug or closure 402 may have a profile larger than theshroud 400, or it may comprise serrations or bumps, to provide enhancedgrip for removal and to remind the user that it should be removed priorto inserting it into the body lumen or cavity. The shroud 400 serves toprotect the distal sheath tube 322 during shipping and handling and canhelp maintain the distal sheath tube 322 in its tightly folded andminimum diameter configuration during sterilization and for extendedperiods of storage and shipping. The shroud 400 ideally encloses theentire fully collapsed distal sheath tube 322, although less than fullenclosure may also be functional. The shroud 400 may further comprisecolors that differentiate it from the rest of the sheath 300, includingtransparent, translucent, fluorescent, or bright colors of orange,green, red, and the like. The shroud 400 may further comprise a label ortag with warnings that it must be removed prior to use of the sheath 300on a patient. The label or tag can be integral to the shroud 400 or theplug or closure 402.

FIG. 5A illustrates a side view of another embodiment of asheath-dilator system 500 comprising a proximal section 502 and a distalsection 504. The distal section 504 comprises a length of dilator tubing318, a dilator balloon 320, and a longitudinally folded sheath tube 510.The distal section 504 further may comprise longitudinal runners 506 orflutes 520 separated by longitudinal slots or depressions 508. Theproximal section 502 comprises a proximal sheath cover 512, a sheath hub308, and a dilator hub 316, further comprising a guidewire port 408 anda balloon inflation connector 330. The sheath and catheter hubs 308, 316can be arranged as described above.

Referring to FIG. 5A, the folded layer 510 is similar to the wall 306 ofthe sheath 300 of FIG. 3A. The folded layer 510 can be affixed, at itsproximal end, to the distal end of the proximal sheath cover 512, whichis non-expansible and surrounds the sheath 500 at its proximal end. Thefolded sheath tube 510 can also be integral to the proximal sheath cover512, although the two regions may have different characteristics. Theinternal lumen of the folded sheath tube 510 is operably connected tothe inner working lumen of the proximal sheath cover 512. The foldedsheath tube 510 is constructed from materials that are plasticallydeformable, or malleable, such that the circumference is irreversiblyincreased by expansion of the dilator balloon 320 and the outward forcescreated thereby. The wall thickness of the folded sheath tube 510 ispreferably generally constant as the folded sheath tube 510 is dilated.The folded sheath tube 510, once dilated, will generally providesufficient hoop strength against collapse that it keeps surroundingtissues open. The optional longitudinal runners 506 or flutes 520,separated by the slits or depressions 508, provide a reduced frictiontrack for the passage of instrumentation within the folded sheath tube510. The runners 506 or flutes 520 can be fabricated from materials suchas, but not limited to, PTFE, FEP, PET, stainless steel, cobalt nickelalloys, nitinol, titanium, polyamide, polyethylene, polypropylene, andthe like. The runners 506 or flutes 520 may further provide columnstrength against collapse or buckling of the folded sheath tube 510 whenmaterials such as calcific stones or other debris is withdrawnproximally through the sheath 500. The runners 506 or flutes 520 may befree and unattached, they may be integral to the ID material, or theymay be affixed to the interior of the folded sheath tube 510 usingadhesives, welding, or the like. In the case of flutes 520, thestructure can be integrally formed with the folded sheath tube 510, suchforming generally occurring at the time of extrusion or performed lateras a secondary operation. Such secondary operation may includecompressing the folded sheath tube 510 over a fluted mandrel under heatand pressure. The flutes 520 may advantageously extend not only in thedistal region 504 but also in the interior of the proximal part of thesheath tubing, and/or, but not necessarily the hub 308.

The guidewire port 408 is generally configured as a Luer lock connectoror other threaded or bayonet mount and the guidewire is insertedtherethrough into the guidewire lumen of the dilator tubing 318 to whichthe guidewire port 408 is operably connected. The guidewire port 408 ispreferably integrally fabricated with the dilator hub 316 but may be aseparately fabricated item that is affixed to the dilator hub 316. ATuohy-Borst or other valved fitting is easily attached to suchconnectors to provide for protection against loss of fluids, even whenthe guidewire is inserted.

FIG. 5B illustrates the sheath 500 of FIG. 5A wherein the balloon 320has dilated the distal section 504 diametrically. The proximal sheathcover 512 is unchanged but the longitudinal runners 506 or flutes 520have moved apart circumferentially and the longitudinal slits ordepressions 508 have become wider through unfolding or separating. Thefolded sheath tube 510 of the distal section 504 has become unfoldedpermanently or substantially permanently to an increased diameter.Because of reinforcements within the folded sheath tube 510, or becauseof internal strength and malleability or plastic deformation, theresultant distal section 504 is well supported in the open position bythe folded sheath tubing 510 for subsequent instrument passage.

FIG. 5C illustrates a lateral cross-section of the distal end 504 of thesheath 500. In this embodiment, the folded sheath tube 510 covering thedistal section 504 is fabricated with flutes 520 on the interior, orexterior, surface. Interior flutes 520 are the preferred embodiment inthis case. The flutes 520 represent longitudinally running increases inwall thickness, or high spots, of the folded sheath tube 510 which areseparated by longitudinally running regions of decreased wall thickness522 or depressions. The flutes 520 are generally integral to the foldedsheath tube 510. The flutes 520 are generally created by fabricating anextrusion die with slots that permit the polymer to extrude with ridgesthereon. The flutes 520 may facilitate folding and minimize damage tooptical scopes, such as ureteroscopes, angioscopes, endoscopes, and thelike, when inserted therethrough, due to debris scratching the lens whenthe scope is advanced or retracted. When the folded sheath tube 510 isdilated, the region of decreased wall thickness 522 between the flutes520 will preferentially unfold because of the increased strength of theflutes 520.

FIG. 6A illustrates a side cutaway view of another embodiment of anexpandable sheath 600 comprising a proximal sheath tube 602 and a distalsheath tube 604. The proximal sheath tube 602 further comprises aproximal reinforcing layer 612, an inner layer and an outer layer. Thedistal sheath tube 604 further comprises a longitudinal fold 606, adistal reinforcing layer 610, an outer layer 608, an inner layer 614,and a dilatation balloon 320. The sheath 600 also includes sheath andcatheter hubs 308, 316 that can be arranged as described above.

Referring to FIG. 6A, in one embodiment, the proximal reinforcing layer612 embedded within the proximal sheath tube 602, which is a compositestructure, preferably formed from an inner and outer layer. The proximalreinforcing layer 612 can be a coil, braid, or other structure thatprovides hoop strength to the proximal sheath tube 602. The proximalreinforcing layer 612 can be fabricated from metals such as, but notlimited to, stainless steel, titanium, nitinol, cobalt nickel alloys,gold, tantalum, platinum, platinum iridium, and the like. The proximalreinforcing layer 612 can also be fabricated from polymers such as, butnot limited to, polyamide, polyester, and the like. Exemplary polymersinclude polyethylene naphthalate, polyethylene terephthalate, Kevlar,and the like. The proximal reinforcing layer 612, if it comprises metal,preferably uses metal that has been spring hardened and has a springtemper.

Further referring to FIG. 6A, the distal sheath tube 604 is constructedfrom a composite construction similar to that of the proximal sheathtube 602. The distal reinforcing structure 610, however, is preferablynot elastomeric but is malleable. The distal reinforcing structure 610is preferably a coil of flat wire embedded between the inner layer 614and the outer layer 608. The crease or fold 606 runs longitudinally thelength of the distal sheath tube 604 and is the structure that permitsthe distal sheath tube 604 to be compacted to a smaller diameter thanits fully expanded configuration. There may be one fold 606, or aplurality of folds 606. The number of folds 606 can range between 1 and20, and preferably between 1 and 8, with the sheath tubing 604bendability and diameter having an influence on the optimal number offolds 606.

The construction of the distal sheath tube 604 can comprise a coil ofwire with a wire diameter of 0.001 to 0.040 inches in diameter andpreferably between 0.002 and 0.010 inches in diameter. The coil can alsouse a flat wire that is 0.001 to 0.010 inches in one dimension and 0.004to 0.040 inches in the other dimension. Preferably, the flat wire is0.001 to 0.005 inches in the small dimension, generally oriented in theradial direction of the coil, and 0.005 to 0.020 inches in width,oriented perpendicular to the radial direction of the coil. The outerlayer 608 has a wall thickness of 0.001 to 0.020 inches and the innerlayer 614 has a wall thickness of between 0.001 and 0.010 inches. Thewire used to fabricate the coil can be fabricated from annealedmaterials such as, but not limited to, gold, stainless steel, titanium,tantalum, nickel-titanium alloy, cobalt nickel alloy, and the like. Thewire is preferably fully annealed. The wires can also comprise polymersor non-metallic materials such as, but not limited to, PET, PEN,polyamide, polycarbonate, glass-filled polycarbonate, carbon fibers, orthe like. The wires of the coil reinforcement can be advantageouslycoated with materials that have increased radiopacity to allow forimproved visibility under fluoroscopy or X-ray visualization. Theradiopaque coatings for the coil reinforcement may comprise gold,platinum, tantalum, platinum iridium, and the like. The mechanicalproperties of the coil are such that it is able to control theconfiguration of the fused inner layer 614 and the outer layer 608. Whenthe reinforcing layer 610 is folded to form a small diameter, thepolymeric layers, which can have some memory, do not generatesignificant or substantial springback. The sheath wall is preferablythin so that it any forces it imparts to the tubular structure areexceeded by those forces exerted by the malleable distal reinforcinglayer. Thus, a peel away or protective sleeve is useful but notnecessary to maintain the collapsed sheath configuration.

The inner layer 614 and the outer layer 608 preferably comprise someelasticity or malleability to maximize flexibility by stretching betweenthe coil segments. Note that the pitch of the winding in the distalreinforcing layer 614 does not have to be the same as that for thewinding in the proximal reinforcing layer 612 because they havedifferent functionality in the sheath 600.

FIG. 6B illustrates a cutaway sectional view of the sheath 600 of FIG.6A following expansion by the balloon 320. The proximal sheath tube 602has not changed its diameter or configuration and the reinforcing layer612 is likewise unchanged in configuration. The distal tube 604 hasbecome expanded diametrically and the crease or fold 606 of FIG. 6A isnow substantially removed. In the illustrated embodiment, due to stresshardening of the reinforcing layer and residual stress in the foldedinner layer 614 and outer layer 608, some remnant of the fold 606 maystill exist in the distal tube 604. The expansion of the sheath 600 inthis configuration can be accomplished using a balloon 320 with aninternal pressure ranging between 3 atmospheres and 25 atmospheres. Notonly does the balloon 320 impart forces to expand the distal sheath tube604 against the strength of the reinforcing layer 610 but it also shouldpreferably overcome any inward radially directed forces created by thesurrounding tissue. In an exemplary configuration, a sheath 600 using aflat wire coil reinforcing layer 610 fabricated from fully annealedstainless steel 304V and having dimensions of 0.0025 inches by 0.010inches and having a coil pitch of 0.024 inches is able to fully expand,at a 37-degree Centigrade body temperature, to a diameter of 16 Frenchwith between 4 and 7 atmospheres pressurization. The inner layer 614 ispolyethylene with a wall thickness of 0.003 to 0.005 inches and theouter layer 608 is polyethylene with a wall thickness of 0.005 to 0.008inches. The sheath is now able to form a path of substantially uniforminternal size all the way from the proximal end to the distal end and tothe exterior environment of the sheath at both ends. Through this path,instrumentation may be passed, material withdrawn from a patient, orboth. A sheath of this construction is capable of bending through aninside radius of 1.5 cm or smaller without kinking or becomingsubstantially oval in cross-section.

FIG. 7A illustrates a side view of another embodiment of an expandablesheath 700 comprising a proximal end 702 and a distal end 704. Thesheath 700 further comprises an outer covering 706, a dilator shaft 708,a support frame 710, a dilatation balloon 712, a sheath hub 714, adilator hub 716, a guidewire port 720, and a balloon inflation port 722.The distal end 704 has a reduced diameter relative to that of theproximal end 702.

Referring to FIG. 7A, the support frame 710 in the illustratedembodiment comprises a scaffold structure similar to a stent such asthat used for treating stenoses in the coronary arteries. The supportframe 710 is embedded within, or resides interior to and against, theinner diameter of the outer covering 706. The support frame may befabricated from stainless steel, titanium, martensitic nitinol, gold,platinum, tantalum, or other materials commonly used to fabricatecardiovascular stents. The support frame may be fabricated from wire, itmay be laser cut from a tube or sheet of metal, or it may bephoto-etched, mechanically machined, or machined using electrondischarge methodology. The support frame, in an embodiment, is malleableand remains in the state to which it is dilated by the dilatationballoon 712. The support frame is preferably radiopaque under thecircumstances in which it is used in vivo and may be fabricated from,alloyed with, or coated with materials such as gold, platinum, platinumiridium, or tantalum. The support frame wall thickness can range from0.002 to 0.025 inches and preferably be between 0.003 and 0.012 inches.The support frame preferably comprises structures that permitflexibility. Such flexibility enhancing structures include disconnected“Z” or diamond-shaped ring segments, ring segments connected by abackbone or alternating backbone of wire, continuous undulating spirals,and the like. The outer covering is either unfurling, malleablyexpansible, or elastomeric. An exemplary expansible outer covering 706comprises a low-density polyethylene disposed so that it embeds thestent. Another expansible outer covering 706 comprises a polyurethane,silastic or thermoplastic elastomer sleeve disposed around andfrictionally covering the support frame 710. The outer covering 706 mayfurther comprise an inner layer that is relatively low in slidingfriction such as, but not limited to, high density polyethylene, FEP,PTFE, or the like. A furled outer covering 706 may be fabricated fromstretch blow-molded PET. The outer covering 706 may be coated on itsinterior, exterior, or both, by silicone slip agents, hydrophilichydrogels, or the like to minimize friction in passing the catheterthrough the body lumen as well as passage of instruments therein.

FIG. 7B illustrates the sheath 700 of FIG. 7A wherein the support frame710 has become expanded by the dilatation balloon 712 having beenpressurized by fluid injected into the inflation port 722 on the dilatorhub 716 and transmitted to the balloon 712 through the dilator shaft708. The support frame 710, at the distal end 704, has malleablyexpanded and holds the outer covering 706 in its radially-expandedconfiguration.

Referring to FIG. 7B, the support frame 710 is affixed to the distal endof the proximal portion 702 of the sheath 700. The support frame 710 maybe fully expanded at this proximal end even prior to expansion, as inFIG. 7A, and then neck down in the distal portion 704. Once expanded,the support frame 710 and the outer covering 706 have a generallycontinuous diameter and through lumen passing all the way from theproximal most portion of the sheath 700 to the distal end thereof. Theouter covering 706 in the distal portion 704 will have stretched orunfurled to take on its larger diameter configuration. The recoverystrength of the outer covering 706 is preferably such that it does notimpart restorative forces greater than the resistive forces generated bythe malleably expanded support frame 710. The distal region 704 remainsdilated once the dilatation balloon 712, the dilator shaft 708, thedilator hub 716, and the inflation port 722 have all been removed fromthe sheath 700. Thus, a large central lumen is generated within thesheath 700.

FIG. 8A illustrates a side view of another embodiment of an expandablesheath 800 comprising a proximal region 802 and a distal region 808. Inthis embodiment, the proximal region 802 further comprises a braidedreinforcement 804, a proximal sheath covering 806, and a proximal innerlayer 832. The distal region 808 of this embodiment further comprises adistal sheath covering 810 and a distal reinforcement 812, and a distalinner layer 830. The distal region 808 has a reduced diameter relativeto that of the proximal region 802 because the distal sheath covering810 has been folded or furled to form one or more longitudinal creasesor pleats 820. A transition region 822 connects the proximal sheathcovering 806 and the distal sheath covering 810. Also shown is thedilator hub 316 and the guidewire access port 332.

Referring to FIG. 8A, the distal sheath region 808, which comprises thedistal sheath covering 810, begins approximately at the transitionregion 822. The distal sheath covering 810 is thin-walled material thatis folded into a plurality of pleats 820. The distal sheath covering 810can be fused to a distal inner liner 830 and further cover or encompassa reinforcing layer 812. The distal sheath covering 810 is fabricatedfrom materials such as, but not limited to, PET, polyethylene,polypropylene, Hytrel, Pebax, polyimide, polyamide, HDPE, and the like.The wall thickness of the distal sheath covering 810 ranges from 0.001to 0.020 inches. The distal sheath covering 810 may be heat set, orcross-linked by irradiation (e.g. gamma radiation or electron beamradiation), to sustain the pleats, creases, or folds 820. The distalsheath covering 810 is affixed to the distal end of the proximal sheathcovering 806 by welding or adhesive bonding. The proximal sheathcovering 806 may be a unitary polymer tube fabricated from materialssuch as, but not limited to, Hytrel, Pebax, polyethylene, polyurethane,FEP, PTFE, or the like. The proximal sheath covering 806 may further bea composite reinforced structure with an internal coil or braidreinforcement 804 surrounded by polymers. The polymer on the proximalinner layer 832 may preferentially be a different polymer than thatdisposed on the exterior of the proximal sheath covering 806. Gammaradiation, electron beam radiation, proton irradiation, neutronirradiation, plasma discharge or the like may be used to modify thecharacteristics of the polymers used on the sheath, such as increasingtheir tensile strength, adhesiveness between layers, etc. The transitionregion 822 is designed to reduce or minimize stress risers that wouldoccur if the proximal region 802 were butt-joined to the distal region808. To optimize the transition 822, the proximal region 802 and thedistal region 808 are feathered or serrated and the serrationsinterdigitated to generate a smooth segue between the mechanicalproperties of the proximal region 802 and the distal region 808. Theserrations are preferably triangular in shape and between 0.10 and 5.00centimeters long. The number of serrations can range between 1 and 20.

FIG. 8B illustrates an enlarged view of the distal tip of the distalregion 808 of the sheath 800. The distal region 808 further comprisesthe distal sheath covering 810, the distal reinforcing layer 812, andthe distal inner layer 830. The distal reinforcing layer 812, in thiscase a coil of malleable metal, further comprises a hoop end structure834 and a weld 836. The distal region 808 further comprises anexpandable radiopaque marker 838. The hoop end structure 834 is createdby bring the final turn of the coil comprising the distal reinforcinglayer 812 around and joining it to the prior coil using the weld 836.The weld 836 can also be an adhesive bond, crimp joint, or the like. Theweld 836 is advantageously shaved or configured so as not to create asubstantial bump, which could poke or project through the distal innerlayer 830 or the distal sheath covering 810. The expandable radiopaquemarker 838 can be comprised of malleable wire such as gold, tantalum,platinum, or the like. A plurality of turns of the wire, generallynumbering between 1 and 20 turns, are sufficient to comprise a visibleradiopaque marker 838. The radiopaque wire can be either flattened orround wire with a major dimension of between 0.001 inches and 0.020inches. The wire is preferably foldable so that it can be creasedlongitudinally and collapsed diametrically along with the rest of thedistal region 808. The multiple turn wire radiopaque marker 838 isadvantageous, relative to other marker types because it embeds well inthe polymer of the distal sheath covering 810 and offers less resistanceto unfolding and expansion than would a band or solid ring.

FIG. 9A illustrates an embodiment of a collapsed, radially expandablesheath 900 comprising a large step transition 902 between the foldedballoon 320 and the distal sheath covering 810. The sheath 900 furthercomprises a dilator shaft 318, to which the folded balloon 320 isaffixed. Because of various folding configurations for the distal sheathcovering 810, such step transitions 902 can occur. The step transitions902, however, may catch on tissue as the sheath 900 is being advancedtransluminally, thus impeding progress and potentially causing injury ortrauma to the lumen wall. For example, referring to FIGS. 1 and 9A,during ureteral access procedures, the step transition 902 can catch onthe tissues at the entrance 114 to the ureter 106 where the ureter 106meets the bladder 104. Thus, in some embodiments, it is advantageousthat a fairing be provided to minimize or eliminate the step transition902. The sheath 900 further comprises a transition zone 910 between thedistal sheath covering 810 and the proximal sheath covering 916,comprising distal chevrons 914 and proximal chevrons 912. The number ofchevrons can vary between 2 and 30 with a preferred range of 4 to 16.The chevrons 912 and 914 can be welded, bonded, or fused and the taperednature of the chevrons 912 and 914 enhances a smooth transition betweenthe distal sheath covering 810 and the proximal sheath covering 916. Inan embodiment, the distal sheath covering 810 and the proximal sheathcovering 916 are fabricated from extruded polyolefin such aspolyethylene. Reinforcements within the sheath coverings 810 and 916 caninclude coils, sleeves, tape, windings, braids, etc. and these are alsotransitioned within the chevrons 912 and 914 of the transition zone 910or they are terminated outside the transition zone 910 so that noreinforcement exists within the transition zone 916. The chevrons 912and 914 become distorted when the distal sheath covering 810 is foldedor compressed longitudinally to its small diameter configuration. Thedilator balloon (not shown) preferably extends proximally of the mostproximal point of the transition zone 910.

FIG. 9B illustrates a radially expandable sheath 900 comprising afairing sleeve or distal shroud 904. In an embodiment, the distal shroud904 is permanently affixed to the exterior of the dilator shaft 318 orthe balloon 320 bond area. The distal shroud 904 may be rigid or it maybe flexible or elastomeric. The distal shroud 904 covers the distalsheath covering 810 and holds the distal end of said covering 810compressed against the dilator shaft 318 and the folded dilatationballoon 320. In another embodiment, the distal shroud 904 extendssubstantially to, but does not cover, the distal sheath covering 810 andserves as a nosecone for the distal sheath covering 810. In thisembodiment, it is preferable that the gap between the proximal end ofthe distal shroud 904 and the distal end of the distal sheath covering810 be minimized to prevent tissue from protruding therein. The distalshroud 904 may be fabricated from C-Flex, polyurethane, siliconeelastomer, polyolefin, Hytrel, polyvinyl chloride, and the like. Thedistal shroud 904 can also be fabricated from bio-resorbable or waterdissolvable materials such as, but not limited to polylactic acid,polyglycolic acid, sugars, carbohydrates, or the like. Resorbablematerials would be useful if the shroud 904 were to inadvertently comefree from the dilator shaft 318 or balloon 320 and was left behind inthe patient. The distal shroud 904 can further comprise radiopaquefillers such as, but not limited to, barium or bismuth salts, ortantalum powder. The distal shroud 904 can also comprise a radiopaquemarker fabricated separately from platinum, gold, tantalum, iridium, orthe like. The separate radiopaque marker can be insert molded, as in thecase of a ring or band, or wound as in the case of wire, etc. The distalshroud 904 may be injection molded, liquid injection molded, thermallyformed, or cut from an extrusion or dip-coated structure. The distalshroud 904 is preferably conical or tapered so that its diameterincreases moving from the distal to the proximal direction. The distalshroud 904 may further be asymmetric or non-round in lateralcross-section to mate to the step transition 902, which may be larger inone circumferential location, than in another location. The distalshroud 904 generally has an undercut at its proximal end to allow theshroud to extend over the sheath covering 810, although it could alsojust butt up against the distal end of the sheath covering 810, withoutoverlap. The distal shroud 904 is firmly bonded to the dilator shaft 318or the balloon 320 so that it does not inadvertently come free from thesheath 900, a situation that could result in clinical complications. Thebonding of the distal shroud 904 to the balloon 320 or the dilator shaft318 may comprise heat welding, ultrasonic welding, adhesives, mechanicalinterlock, or a combination thereof. In an embodiment, the distal shroud904 will deform and expand outward with the balloon 320, thus pullingaway from the distal end of the distal sheath covering 810. When thedistal sheath covering 810 has been expanded and the balloon 320subsequently deflated, the distal shroud 904 will re-compress radiallywith the balloon 320 so that it can be withdrawn proximally through theinternal lumen of the distal sheath covering 810.

The distal shroud 904 may further comprise an inner spacer (not shown)to prevent inadvertent withdrawal of the obturator or dilator, andshroud 904. A mechanism can be provided to allow the shroud to beadvanced distally to release the sheath covering 810 so that it canexpand. The inner spacer can further comprise, on its proximal end, ataper to facilitate proximal withdrawal into the sheath cover 810. Thedistal shroud 904 can be made thin and flexible so that it everts whenthe dilator is withdrawn proximally relative to the sheath covering 810.The inner spacer may further comprise an undercut or relief on itsdistal end, which allows the shroud to maintain a low profile, followingeversion, prior to or during proximal withdrawal.

FIG. 9C illustrates the sheath 900 of FIG. 9B, following expansion,comprising a distal sheath covering 810, a proximal sheath covering 916,an expanded dilatation balloon 320, a dilator shaft 318, and a distalshroud 904. The sheath 900 further comprises the transition zone 910,the proximal chevron 912, and the distal chevron 914. The proximal partof the distal shroud 904 has been shown in breakaway fashion to revealthe balloon 320. The proximal end of the distal shroud 904 has expandedelastomerically with the balloon 320 and, in so doing, has retracteddistally from covering or overlapping the distal end of the distalsheath covering 810. Attachment of the distal end of the distal shroud904 to the balloon 320 or the dilator shaft 318 prevents motion of thedistal end of the distal shroud 904 in the proximal direction. Followingthe next step, which is deflation of the balloon 320, the elastomericdistal shroud 904 will reduce in diameter and be able to be withdrawnthrough the central lumen of the distal sheath tube whose outer layer isthe covering 810. The transition zone 910 has expanded and becomesubstantially of constant diameter since the distal sheath covering 810has been radially expanded. The proximal chevrons 914 and the distalchevrons 912, which are interdigitated and affixed by fusing, gluing,bonding, welding, sleeving, or clamping together, are generallyundistorted and form a substantially even zig-zag pattern with asubstantially smooth gradual transition in properties when going fromthe proximal sheath tubing 916 to the distal sheath covering 810. Thetransition zone 910 thus comprises a plurality of tapered,interdigitated chevrons 912 and 914 of the proximal region and thedistal region, said regions being at least partially affixed togetheralong the edges of the chevrons 912 and 914.

In another embodiment, the distal end of the distal sheath covering 810comprises extra material (not shown) that extends distally toward theexposed dilator shaft 318. This extra material can be symmetricallydisposed around the circumference of the distal sheath covering 810 orit can be asymmetrically distributed so as to form a canopy that extendsonly over half of the sheath distal end. Following folding, the canopycan be further heat set or formed to form a fairing to minimize oreliminate the step transition 902. While the coil or braid reinforcementcan also support the transition canopy, it is preferable that anyinternal reinforcement not extend into the canopy or distal sheathcovering extension. In an embodiment where the reinforcing layer is abraided structure, a pick count ranging between 10 and 30 picks per inchand between 8 and 42 carriers of strand is appropriate for thisapplication.

Referring to FIGS. 3A, 8A, and 9A, in an embodiment, the dilator shaft318 can comprise a central through lumen 334, generally 0.010 to 0.060inches in diameter that is operably connected to the guidewire port 332on the dilator hub 316. The dilator shaft 318 is affixed to the dilatorhub 316 by insert molding, welding, adhesive bonding, or the like. Thedilator hub 316 can be advanced forward causing the dilator shaft 318 toadvance relative to the distal sheath covering 810. The shroud 904 pullsforward therewith and no longer surrounds the exterior of the distalsheath covering 810. The sheath covering 810 is now free to expand byunfurling the pleats or folds 820 and serve as potential space forinstrumentation once the obturator shaft 318 and its associatedcomponents are withdrawn from the sheath 900. In another embodiment, theshroud 904 is evertable and the dilator hub 316 is withdrawn proximallyto simply pull the shroud 904 off the sheath covering 810 and outthrough the central lumen of the sheath 900. The shroud 904, in thisembodiment, may be fabricated from metals such as stainless steel orfrom polymers such as C-Flex, polypropylene, polyethylene, polyurethane,silicone elastomer, and the like.

FIG. 10A illustrates a lateral cross-section of an embodiment of thedistal tubing 1008, which can be used in combination with the sheathembodiments described above. The distal tubing, in this embodiment, isextruded or formed with thin areas 1032 and normal wall 1030. Theillustrated embodiment shows two thin areas 1032 prior to folding. Thespacing and magnitude of the thick and thin areas do not necessarilyhave to be uniformly placed or equally sized. The thin areas can be usedto enhance the ability to form tight folds for diameter reduction.

FIG. 10B illustrates the distal tubing 1008 of FIG. 10B after it hasbeen folded longitudinally. Other folds, including Napster™-type styles,star shapes, clover-leafs, folded “W”s, and the like, are also possible.Such profiling can be performed on tubing fabricated from materials suchas, but not limited to, polyethylene, PTFE, polyurethane, polyimide,polyamide, polypropylene, FEP, Pebax, Hytrel, and the like, at the timeof extrusion. The distal tubing 1008 would then be used, as-is, or itwould be built up onto a mandrel with other layers as part of acomposite tube. The composite tube can include coil, braid, or stentreinforcement. The thin areas 1032 facilitate tight folding of the layer1008 and minimize the buildup of stresses and strains in the materialthat might prevent it from fully recovering to a round shape followingunfolding.

FIG. 10C illustrates a lateral cross section of the distal end of thesheath 600 of FIG. 6A. In the illustrated embodiment, the balloon 320has been folded to form four longitudinal creases, furls, or pleats1020. The dilator shaft 318 remains in place in the center of theballoon 320 and is fluidically sealed to the balloon 320 at the distalend of said balloon 320. The compressed sheath covering 1008 surroundsthe folded balloon 320. When the balloon 320 is expanded under pressurefrom an external pressure source, the balloon expands the sheathcovering 1008 to a larger diameter. The sheath covering 1008 maintainsthat configuration held in place by the malleable sheath reinforcementor by the malleable nature of the unitary sheath covering 1008, should aseparate reinforcement not be used.

FIG. 10D illustrates a lateral cross-section of an embodiment of asheath tube comprising an inner layer 1052, a reinforcing layer 1056, anelastomeric layer 1054, and an outer layer 1050. The elastomeric layer1054 can be disposed outside the reinforcing layer 1056, inside thereinforcing layer 1056, or both inside and outside the reinforcing layer1056. The elastomeric layer 1054 is fabricated from silicone elastomer,thermoplastic elastomer such as C-FIex™, a trademark of ConceptPolymers, polyurethane, or the like. The hardness of the elastomericlayer 1054 can range from Shore 10A to Shore 90A with a preferred rangeof Shore 50A to Shore 70A. The inner layer 1052 and the outer layer 1050are fabricated from lubricious materials such as, but not limited to,polyethylene, polypropylene, polytetrafluoroethylene, FEP, materials asdescribed in FIG. 8A, or the like. The inner layer 1052 and the outerlayer 1050 can have a thickness ranging from 0.0005 inches to 0.015inches with a preferred range of 0.001 to 0.010 inches. The elastomericlayer 1054 can range in thickness from 0.001 inches to 0.015 inches witha preferred range of 0.002 to 0.010 inches. The reinforcing layer 1056is as described FIG. 6A. This construction is beneficial for both theproximal non-expandable region and the distal expandable region of thesheath. In an embodiment, the C-Flex thermoplastic elastomer is used forthe elastomeric layer 1054 because it fuses well to the polyethyleneexterior layer 1050. This embodiment provides for improved kinkresistance, improved bendability, and reduced roughness or bumpiness onthe surface of the sheath where the elastomeric layer 1054 shields thereinforcing layer 1056. This embodiment provides for a very smoothsurface, which is beneficial on both the interior and exterior surfacesof the sheath.

FIG. 10E illustrates a lateral cross-sectional view of an embodiment ofan expandable sheath distal section 1040. The sheath distal section 1040comprises a dilator tube 318, a dilator balloon, 320, and an outersheath covering 1042, further comprising a first fold 1044 and a secondfold 1046. For sheaths with a wall 1042 thickness of about 0.008 to0.020, it is useful to fold the sheath covering 1042 into two folds 1044and 1046 if the inside diameter of the expanded sheath ranges greaterthan 12 French. If the inside diameter of the expanded sheath covering1042 is less than about 12 French, and sometimes when the sheathcovering 1042 is substantially equal to 12 French, it is preferred tohave only a single fold, either 1044 or 1046. If the diameter of thesheath covering 1042 is greater than 18 French, or the wall thickness ofthe sheath covering 1042 is less than the range of about 0.008 to 0.020inches, or both, additional folds can be added.

FIG. 11A illustrates a side view of another embodiment of an expandablesheath 1100 comprising a proximal end 1102 and a distal end 1104. Thesheath 1100 further comprises an outer covering 1106, a dilator shaft1108, a split-ring support frame 1110, a dilatation balloon 1112, asheath hub 1114, a dilator hub 1116, a guidewire port 1120, and aballoon inflation port 1122. The distal end 1104 has a reduced diameterrelative to that of the proximal end 1102.

Referring to FIG. 11A, the split-ring support frame 1110 is a malleablestructure that can be dilated by forces exerted by the inflated balloon1112. The dilation is the same as that generated by the sheath 700 ofFIGS. 7A and 7B. The split-ring support frame can be fabricated fromwire or from flat sheets of metal, from wires, or from tubes of metal.The preferred metal is selected from materials such as, but not limitedto, cobalt nickel alloys, titanium, tantalum, annealed stainless steelssuch as 316L, 304, and the like. The split ring support frame 1110 isdisposed inside the inner diameter of the distal sheath tubing 1106. Thesplit ring support frame 1110 has the advantage of being inexpensive tofabricate relative to other stent-like support designs. The split ringsupport frame 1110 can be configured as a series of ribs and a backbone,or as a series of staggered backbones to facilitate flexibility alongmore than one axis. Alternatively, in another embodiment, the split ringsupport frame 1110 can be self-expanding. The preferred configurationfor the distal sleeve 1106 is a thin wall polymer that is furled intolongitudinal flutes. The split ring can comprise rings whose endsoverlap circumferentially when the sheath is collapsed diametrically, aswell as being expanded diametrically. Furthermore, the split ringconfiguration can comprise rings that do not overlap in the collapsedconfiguration, the expanded configuration, or both.

FIG. 11B illustrates the sheath 1100 of FIG. 11A wherein the supportframe 1110 has become expanded by the dilatation balloon 1112 havingbeen pressurized by fluid injected into the inflation port 1122 on thedilator hub 1116 and transmitted to the balloon 1112 through the annulusbetween the outer and inner tubes comprising the dilator shaft 1108. Thesplit-ring support frame 1110, at the distal end 1104, has malleablyexpanded and holds the outer covering 1106 in its radially expandedconfiguration. The through lumen of the distal end 1104 is substantiallysimilar to that of the proximal end 1102.

FIG. 12 illustrates another embodiment of the catheter 600, wherein thestep transition 902 of FIG. 9A can be minimized by the inclusion of agel, foam, or liquid-filled sac 1202 within balloon 320 just proximal tothe distal balloon bond 1204, which is the region where the balloon 320is bonded to the dilator shaft 318. When the distal sheath covering 608and the balloon 320 are folded and collapsed, the material within thesac 1202 will remain puffed out and create a fairing within the balloonthat smoothes the transition 902. A key advantage of such an internalfairing is that it cannot become dislodged from the sheath 600. The sac1202 can be free-form, it can be circular in cross-section, or it can benon-circular and oriented to conform to circumferential irregularitiesin the transition 902. In another embodiment, the sac 1202 is filledwith a resilient polymer following assembly of the collapsed sheath tothe folded dilator so that a custom fairing 1202 is created. In yetanother embodiment, there is no sac, but an internal fairing 1202 iscreated using a foam, or a low durometer polymer. This internal fairing1202 is located on the distal dilator shaft 318 inside the balloon 320.This embodiment can further comprise a coating of lubricious materialsuch as silicone elastomer, hydrogel, or the like, on the inside of thesheath tubing 608 or the outside of the balloon 320 to aid in slidingthe balloon with internal fairing proximally out of the sheath tubing608.

Referring to FIG. 12, in another embodiment, once the sheath tubing 608is collapsed around the balloon 320, the balloon 320 is filled at itsdistal end by way of a special filling tube (not shown) that is eitherintegral to, or separate from, the dilator shaft 318. The distal end ofthe balloon 320, in this embodiment, is shaped using an external mold(not shown) during filling. The materials used to fill the balloon 320distal end include, but are not limited to, hardenable liquid polymers,gel, and foam that is injected in a liquid state and then hardens orsets up. The filling tube is removed or closed off and the resin isallowed to set-up, or harden, in the shape of the external mold. Thefilled distal end of the balloon 320 forms a tapered fairing 1202 thatminimizes or eliminates any transitions between the sheath and theballoon. In another embodiment, an external mold is not used but thefilling is performed under visual inspection and correction to generatethe correct shape.

In another embodiment, the dilator shaft 318 is formed with a tailoredbump 1202 that is positioned just proximal to the distal balloon 320 todilator shaft 318 bond. The bump 1202 is configured to form a taper andfairing under the distal shoulder of the balloon 320 that ramps up tomeet the sheath tubing 608 and minimize or eliminate any transitionshoulder. Since a coaxial annulus is used to fill the balloon 320, theproximal balloon bond (not shown) is larger in diameter than the distalballoon bond 1204 and the proximal balloon bond can be slid over thebump allowing the bump to reside within the balloon 320. The bump 1202is created by a thermoforming process either free form, or preferablyusing a mold, internal pressure, and the like. The dilator shaft 318,under the bump 1202 in this embodiment, may be thinned or formed into abulb to create the bump 1202.

FIG. 13A illustrates an embodiment of the proximal end of a radiallyexpandable sheath 1300 for endovascular use further comprising a valve1302 operably connected to the sheath hub 1304 and a hemostatic valve1306 operably connected to the dilator hub 1308. In this embodiment, thevalve 1302 is a duckbill valve, one-way valve, or other sealing-typevalve capable of opening to a large bore and yet closing aroundinstrumentation such as the dilator shaft 1320. The valve 1302 sealsagainst fluid loss from the internal lumen of the sheath 1300 while thedilator hub 1308 is connected to the sheath hub 1304 and after thedilator shaft 1320 has been removed from the sheath 1300. The valve 1302can be integral to the sheath hub 1304, it can be welded or adhered tothe sheath hub 1304, or it can be affixed by a Luer fitting or otherquick connect fitting. The hemostatic valve 1306 is a Tuohy-Borst valveor other valve capable of sealing against a guidewire or smallinstrument and remain sealed after removal of said guidewire or smallinstrument. The hemostatic valve 1306 may further comprise a tighteningmechanism (not shown) to enhance sealing against guidewires or againstan open lumen. The hemostatic valve 1306 can be integral to the dilatorhub 1308, it can be welded or adhered to the dilator hub 1308, or it canbe affixed by a Luer fitting or other quick connect fitting. The valves1306 and 1302 are generally fabricated from polymeric materials and havesoft resilient seal elements disposed therein. The hemostatic valve 1306is intended to minimize or prevent blood loss from vessels at systemicarterial pressure for extended periods of time. The valve 1302 isintended to minimize or eliminate blood loss when instrumentation ofvarious diameters is inserted therethrough.

FIG. 13B illustrates an embodiment of the proximal end of a radiallyexpandable sheath 1310 for laparoscopic use, further comprising a valve1312 operably connected to the sheath hub 1314. The valve 1312 isintended primarily to prevent or minimize the loss of fluids (liquids orgasses) from an abdominal or thoracic cavity. The valve 1312 isgenerally fabricated from polymeric materials and has soft resilientseal elements disposed therein. The valve 1312 can be integral to thesheath hub 1314, it can be welded or adhered to the sheath hub 1314, orit can be affixed by a Luer fitting or other quick connect fitting. Thedilator hub 1308 is also shown.

FIG. 14 illustrates a longitudinal cross-sectional view of the proximalend of an embodiment of an expandable sheath system 1400. The expandablesheath system 1400 comprises a sheath hub 1402, a dilator hub 1404, asheath tube 1424 and a dilator tube 1426. The sheath hub 1402 furthercomprises a proximal port 1406, a distal end 1408, a distal face 1410,and a proximal perimeter 1412. The dilator hub 1404 further comprises anengagement detent 1414, a distal taper 1416, a grip handle 1422, aninflation port 1418, and a guidewire port 1420. The sheath hub 1402 canoptionally comprise one or more fins 1428 which can further comprise oneor more attachment holes or slots 1430.

Referring to FIG. 14, the distal face 1410 is oriented substantiallyperpendicularly to the axis of the sheath tube 1424, but it could alsobe at an angle. The distal face 1410 can have a small round or filletstructure to eliminate any sharp corners where it interfaces to the morecylindrical regions of the sheath hub 1402. The proximal perimeter 1412,in this embodiment, is configured to mate with the engagement detent1414 in the dilator hub 1404, which has a slight undercut and a taperedlead in. The proximal perimeter 1412 can be a continuous bandsurrounding up to 360 degrees of the circumference of the sheath hub1402. The proximal perimeter 1412 is preferably rounded or chamfered toease connection and disconnection with the dilator hub 1404 and itsengagement detent 1414. The sheath hub 1402 and the dilator hub 1404 canbe fabricated from polymers such as, but not limited to ABS,polysulfone, PVC, polyolefin including polyethylene or polypropylene,polyamide, polycarbonate, and the like. In a preferred embodiment, thesheath hub 1402 and the dilator hub 1404 are fabricated from differentpolymers to minimize the risk of blocking.

Referring to FIG. 14, the distal end 1408 of the sheath hub 1402 istapered to an increasingly small diameter moving distally so that thedistal end 1408, as well as the proximal end of the sheath tube 1424,can slip substantially within a body vessel or lumen, for example aurethra. The proximal port 1406 of the sheath hub 1402 can be straight,it can be tapered, or it can have a straight taper to facilitate sealingwith the dilator distal taper 1416. The taper angle can be between 1degree and 20 degrees on each side. The dilator hub knob 1422 isintegral to the dilator hub 1404 and provides an enlargement that can begripped by the user to facilitate separation of the dilator hub 1404from the sheath hub 1402. The dilator hub knob 1422 also can be usedbetween the thumb and a finger or between two fingers to advance theentire assembly or remove the assembly from the patient.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example, thesheath may include instruments affixed integrally to the interiorcentral lumen of the mesh, rather than being separately inserted, forperforming therapeutic or diagnostic functions. The hub may comprise tiedowns or configuration changes to permit attaching the hub to the skinof the patient. The embodiments described herein further are suitablefor fabricating very small diameter catheters, microcatheters, orsheaths suitable for cardiovascular or neurovascular access. Thesedevices may have collapsed diameters less than 3 French (1 mm) andexpanded diameters of 4 to 8 French. Larger devices with collapseddiameters of 16 French and expanded diameters of 60 French or larger arealso possible. Such large devices may have orthopedic or spinal accessapplications, for example. The described embodiments are to beconsidered in all respects only as illustrative and not restrictive.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. In addition, while a number of variations of the invention havebeen shown and described in detail, other modifications, which arewithin the scope of this invention, will be readily apparent to those ofskill in the art based upon this disclosure. It is also contemplatedthat various combinations or subcombinations of the specific featuresand aspects of the embodiments may be made and still fall within thescope of the invention. Accordingly, it should be understood thatvarious features and aspects of the disclosed embodiments can be combinewith or substituted for one another in order to form varying modes ofthe disclosed invention. Thus, it is intended that the scope of thepresent invention herein disclosed should not be limited by theparticular disclosed embodiments described above, but should bedetermined only by a fair reading of the claims that follow.

What is claimed is:
 1. A method of providing access to a body lumen comprising the steps of: inserting a sheath into a body lumen; the sheath having an axially elongate sheath tube with a proximal region, a distal region, and a central through lumen; advancing the sheath to a desired site within the body lumen; occluding the central through lumen with a central obturator during the inserting and advancing of the sheath within the body lumen; dilating the distal region of the sheath to an expanded diameter by inflating a balloon on the central obturator, thereby forming a substantially uniform diameter of the central through lumen throughout an entire length of the central through lumen, including the proximal region and the distal region; collapsing the balloon of the central obturator by an action applied at the proximal end of said central obturator, removing the central obturator from the sheath, inserting a device into the central through lumen of the sheath and advancing it to the desired site, performing a desired operation with the device, and removing the sheath from the patient.
 2. The method of claim 1 wherein the dilating is performed by attaching a liquid-filled inflation device to a balloon inflation port at the distal end of the central obturator and infusing fluid under pressure into the central obturator.
 3. The method of claim 1 wherein the step of collapsing the central obturator comprises withdrawing a plunger on an inflation device to withdraw fluid from the central obturator.
 4. The method of claim 1 wherein a guidewire is advanced to the desired site prior to inserting the sheath into the body lumen.
 5. The method of claim 1 wherein the sheath is advanced over a previously placed guidewire, which guidewire is routed through a lumen in the dilator.
 6. The method of claim 1 wherein the desired site is anatomically distal to the region where the desired operation is intended to be performed.
 7. The method of claim 1 wherein the body lumen is a mammalian urinary tract.
 8. The method of claim 1 wherein the desired site is the mammalian ureter.
 9. The method of claim 1 wherein the sheath further comprises a transition zone comprising proximal and distal chevrons, the chevrons forming a substantially even zig-zag pattern with a substantially smooth gradual transition when undistorted.
 10. The method of claim 1 wherein the sheath further comprises a non-expandable proximal region and a transition zone between the non-expandable proximal region and the distal region, the regions being fused together along edges of chevrons.
 11. The method of claim 1 wherein the sheath further comprises longitudinal running flutes.
 12. The method of claim 11 wherein the flutes reduce friction between an inner layer of the sheath and the instrumentation. 